var a:array[1..1000000] of longint;
    i,n,k:longint;
    
function isPrim(N:longint):boolean;
var i:longint;
begin
  i:=1;
  while (sqr(a[i])<=N) and (N mod a[i]<>0) do inc(i);
  isPrim:=N mod a[i]<>0;
end;    
    
begin
  assign(input, 'ciur.in');
  reset(input);
  assign(output, 'ciur.out');
  rewrite(output);
  readln(K);
  n:=1;
  a[1]:=2;  
  i:=3;
  while i<=K do
  begin
    if isPrim(i)
    then begin
      n:=n+1;
      a[n]:=i;
    end;
    i:=i+2;
  end;
  writeln(N);
end.